In Valeriana, Antirrhinum and Corydalis, the spur is very short, and the corolla or petal is said to be gibbous, or saccate, at the base.

The boghead of Scotland, Autun and New South Wales is regarded by Renault and Bertrand as mainly composed of gelatinous Algae (Piles and Reinschia), having a hollow, saccate thallus formed of a single layer of cells.